Soap stock purification



' P 1941; B. H. THURMAN 2,239,131

SOAP s'rocK PURIFICATION Filed Dec. 18, 1937 3 wug/wbom LAr-JLML 'chea Patented Apr. 22, 1941 2,239,131 SOAP STOCK PURIFICATIQN Benjamin H. Thurman, Bronxville, N. K, assignorto Refining, in Reno, Nev., a corporation of Nevada Application iilecember 18, 1937, Serial N6. 180.621

8 Claims.

This invention relates to soap stock purification and more particularly to a method by which soap stock resulting from the alkali refining of animal and vegetable oils may be treated to remove impurities therefrom.

Such soap stock is produced by adding an alkali, such as caustic soda, to the animal and vegetable oils in sufiicient amount to neutralize the free fatty acid therein and to provide an excess for reaction with coloring. matter. The fatty acids react with the alk li to form soap and there is usually some reaction with neutral oil toflorm additional soap and liberate glycerine. Coloring matter and gums are precipitated alon with the soap. The substances are separated om the refined oil as soap stock. eitherby settling or centrifugal separationusually at a temperature between 100 and 160 F. The soap. stock is ordinarily a viscous, slimy and dark colored material containing soap, uncombined oil, caustic soda solution, phosphatides, glycerine, albuminous or proteinaceous matter and other nonfatty matter. For example, the average composition of cottonseed oil soap stock according to Lewkowitsch is as follows:

Per cent Fatty anhydrides 48.50 Glycerine 3.98 Caustic soda (Na2O) 3.20 Foreign organic matter 5.90

Water 36.0'0 Coloring matter 2.42

Such a mixture is subject tofermentation and decomposition and cannot be kept in storage for any length of time without deterioration. This material has been employed in soap powder or bar soap after being subjected to repeated boili g in soap kettles including the employment of salt or large amounts of a caustic soda to grain out the kettle and cause a partial separation betweenthe soap andimpuritiestherein. The soap lyes resulting from settling operations contain large quantities of organic impurities and considerable soap, as well as gly-' cerine, but have no valu'e'and are sent'into'the sewer;

pounds ofsettledsoap. The resultant soap is This procedure is expensive and time consuming and according to Thomssen and soft bodied and has a characteristic and disagreeable odor. On account of these undesirable properties the use of cottonseed soap stock is limited to soap powders and similar preparation which seldom contain more than 25% soap. Soda ash and other filling materials which disguise the odor, hide the color and also serve to preserve the soap are employed in large amounts. As further stated by Thomssen and. Kemp this soap was made up in cakes and was sold to some extent but in recent years it has fallen in disrepute and little, if any, is made or used in bar form.

In accordance with the present invention cottonseed soap stock, as well as soap stocks from other animal and vegetable oils, is purified by a simple process so as to produce a substantially pure soap stock product, non-odorous and nondecomposable, capable of shipment and of being'incorporated into high quality soaps in proportions as high as 40 to The gums, resins, proteins, and other foreign substances, including coloring matter, are largely removed from the soap stock to produce a relatively high quality soap and also valuable by-products.

It is, therefore, arr-object of the present invention to subject soap stock resulting from Another object of the invention'is to provide a I process of continuously treating soap stock to produce a non-odorous and non-decomposable product, 0

Another object of the invention is to provide a process of treating soap stocks in which impurities therein are broken down into valuable by-productsand removed from the soap stock. Another object of the invention is .to provide a process of treating soap stock in which the soap stock is subjected to high temperatures and pressures and impurities removed therefrom in vapor form. i I J Another object of the invention is to provide a processby which substantiallyall of the water is removed from the soap stock such that the soap stock will notferment or decompose during storage or shipment.

, Another objectof the invention is to provide an improved soap stock which is-substantially pulley l2.

dehydrated and which will'not ferment or decompose during storage or shipment.

Another object of the invention is to provide an improved soap stock substantially free of odorous and putrefiable materials.

. A further object of the invention is to provide an improved soap stock relatively free of impurie ties and capable of being employed as soap or being incorporatedinto high quality soap products in large proportions. I

A still further object of the invention is to provide a continuous process of making a high quality soap product containing large proportions of soap obtained from soap stock. I

In accordance with the present invention the soap stock may be subjected to high temperatures and pressures for suflicient length of time to break down impurities, such as proteins, etc.', into compounds of less molecular weight so as to render them capable of vaporization or of being dissolved in water. The heated soap stock may then be introduced into a vaporizing chamber at a lower pressure to vaporize the impurities as well as water from said soap stock. Suflicient alkali may be introduced into the soap stock to saponify all of the neutral oil or other fatty material in the soap stock during the process so that a com pletely saponified product results. The process is preferably carried out as a continuous process and will be described in connection with a suitable apparatus capable'of carrying out such a continuous process. Such an apparatus is diagrammatically shown in the accompanying drawing.

Referring to the drawing, l indicates a mixing receptacle in which the soap stock is mixed with a suitable viscosity reducing material, such as,v

steam, water or caustic soda solution with or without additional fat or fatty acids, so as to render the same capable of being pumped through the system for treating the soap stock. This mixer may be of any suitable construction such as amechanlcal agitator or colloid mill for effectively mixing the water or caustic soda solution with the soap stock. By way of example, the mixer I0 is shown as a conventional mechanical agitator provided with paddles or. impellers ll driven from any suitable source of power by a The mixer may be surrounded by a heating jacket l3 so as to raise the temperature of the materials in the mixer In to reduce the viscosity of the same, or live steam or other heating medium may be introduced into the mixer l0 through a pipe I4 so as to directly contact the contents of the mixer to heat the same. The mixer It may be of large size and employed as a batch mixing device into which a quantity of soap stock is introduced and sufficient water or alkali solution added through the pipe H to give a proper consistency of soap stock and the resultant mixture continuously pumped from the mixer by the pump I5 and through a heating device shown as a coil [6. When employed as a batch mixing device, the agitators I I of the mixer II) are kept running during the withdrawal of material from the mixer so as maintain a substantially uniform mixture leaving the mixer l0 and entering the coil Hi. If desired, the soap stock in the mixer may be given one or more preliminary washes and impurities removed through pipe 16.

Alternatively soap stock from a refining process may be-continuously introduced into the mixer Ill from the spout ll of a continuous centrifugal separator l8 forming part of a refining process.

In such a centrifugal separator the alkali treated oil can be continuously separated from the soap stock, the soap stock discharged as a heavy eflluent from the spout l1 and the refined oil as a lighter effluent from the spout 19. Water or caustic soda solution can also be introduced in proper proportions through the pipe 14' into the mixer l0 so that the mixer functions as a continuous niiixer, in which case it may be of relatively small 5 ze.

In either a batch or continuous mixing it is preferred to introduce suflicient alkali into the mixer III to completely saponify during the process all of the neutral oil and other}, fatty materials contained in or added to the soap stock, Although there is usually some uncombined alkali in the. soap stock is it usually necessary to add additional alkali if complete saponification is to be effected. Also suflicient water is added either as part of the alkali solution or water alone to produce a pumpable mixture. As will be hereinafterv discussed, water alone may frequently be employed to produce a high quality soap stock even though all of the fatty materials in the soap stock have not been converted into soap.

The fluid mixture of soap stock and water or caustic solution is heated in the heating device l6 under an elevated pressure imposed by the pump l5. Heat can be supplied to the heating coil I6, for example, by a burner 2| for liquid or gaseous fuel. Since a substantial period of time of treatment under pressure and high temperatures is usually required for proper treatment of the soap stock one or more additional flow heating devices, for example, heating coils 22 provided with burners 23, are usually desirable and a second pump 24 may be provided for forcing the -mixture through this second heating coil or cells 22. The heated .mixture is then preferably discharged into an evaporating chamber 25 in which vaporizable materials are separated from the soap stock. The vaporizable materials are withdrawn through 'a pipe 26 to a condenser 21 provided with a receiver 28. If fractional condensation of the vaporizable materials are desired one or more additional condensers 29 provided with receivers 30 may be employed and a vacuum pump 3| is preferably provided for maintaining a vacuum in the evaporating chamber 25, condensers 21 and 29 and receivers 28 and 30.

The evaporating chamber 25 is preferably provided with a heating jacket 32 through which any desired heating medium, such as steam or heated mineral oil, may be circulated by the pipes 33 and 34 so as to maintain the desired temperature in the evaporating chamber 25. In the preferred operation in which the temperatures imparted to the mixture in coil 22 and maintained in the evaporating chamber 25 are sufficient to cause the soap stock to be deposited in the evaporating chamber in substantially anhydrous molten form, the soap stock is. discharged by nozzles- 35 positioned to direct the soap stock against the walls of the chamber. This molten material flows down the walls of the chamber in thin films such that vapors are substantially completely separated therefrom and pass inwardly and upwardly through the center of the evaporating chamber in a substantially unimpeded path. This procedure provides-for substantially no entrainment of liquids or solids in the vapors being removed from the evaporating chamber in the pipe 26. It is, of course, apparent that in certain operations where the temperatures are not sufilcient to maintain the material discharged 'into the evaporating chamber in liquid form, a

orating chamber is directed by the sloping walls 3B of the lower portion of the evaporating chamber into the housing 31 of a screw conveyor 38. The housing 31 of the conveyor communicates with the interior of the evaporating chamber in fluid-tight relationship and in fact forms a part of the evaporating chamber 25. The conveyor 38 is preferably provided with an enlarged shaft portion 39 adjacent its discharge end so as to form a constricted passage 40 between the shaft portion 39 and the conveyor housing 31. A cooling jacket 41 is also preferably positioned around the discharge portion of the conveyor housing 31 so as to cool the materials being discharged and this cooling, in conjunction with the constricted passage 40, forms a vacuum seal for the evaporating chamber 41 while at the same time'providing for the continuous discharge of soap stock therefrom. The discharge end of the conveyor housing 31 is preferably provided with a manually operable valve 42 which may be closed during starting and stopping of the apparatus so as to seal the vacuum when insufficient soap stock for that purpose is present in the constricted passageway 40. This valve is normally maintained open during the continuous operation and such soap stock is continuously discharged frorrr the conveyor housing. I

When it is desired to mix purified and substantially completely saponified soap stock with other soap so as to provide a high grade soap mixture having desired physical characteristics, a second conveyor 44 provided with a housing 45 communicating with the housing 3'l of the conveyor 38, may be provided to introduce a mixture of soap and water into the conveyor housing 31 intermediate the evaporating ohamber 25 and the discharge end of the conveyor housing 31. A hopper 46 for such a mixture of soap and water may communicate with the housing 45 of the conveyor 44 so that by adjusting the relative speeds of the conveyors 38 and any desired proportion of soap and water mixture may be introduced into the conveyor housing .31. The conveyor 44 is also preferably provided with an enlarged shaft portion 41 adjacent its discharge end to form a vacuum seal similar to that for the conveyor 38. The soap and water mixture delivered into the conveyor housing '31 may contain'sufiicient water to hydrate the mixture of soap stock and additional soap to the desired de gree such that the mixture maybe extruded from the conveyor housing 31 in bar form suitable for pressing into cakes. Any vapors formed when the mixture of soap and water contacts the heat ed soap stock in the conveyor housing 31 may be withdrawn through a pipe 48 communicating with the condenser 29. The mixture of soap and between the heating coil l6 and the pump 24. This can be accomplished by providing a caustic supply tank and a proportioning pump 52 connected to the soap stock pump l5 through a variable speed device 53 and driving both the pumps 50 and 52 through a variable speed motor 54. Any other suitable means for accurately proportioning the amount of soap stock and alkali solution may be employed.

The alkali solution in the tank 5i may be preheated to any desired temperature below the boil-' ing point of the solution in the tank by means of a heating coil 55 through which any suitable heating medium, such as steam, may be circulated. Also it is preferable to preheat the alkali solution in a flow heating device under pressure such as a coil -56 provided with a burner 51 such that the temperature of the alkali solution mixed with the soap stock in mixer 50 is approximately that of the soap stock from the'coil IS. The mixer 5D in conjunction with the pump 24 provides an efllcient mixing between the soap stock and caustic and in many cases this variation of the process is preferable to mixing the alkali with the soap stock in the mixer in as the additional alkali and soap stock are brought together under heated conditions during flow and a more uni form admixture may sometimes be obtained.

In the simplest and preferred process of the present invention, a quantity of soap stock, such as cottonseed soap stock, is placed in the mixer l0.- This material is extremely viscous and slimy and as indicated above, contains unsaponified oil, phosphatides, proteins, coloring matter, etc. Sufficicnt alkali to completely saponify the saponifiable materials contained in the soap stock is ferred to heat the inixture before it'is withdrawn from the mixer to a temperature appreaching that of the boiling point thereof in 0 order to reduce its viscosity and the amount of heat it is necessary to impart to the mixture in the heating coils, but a lower temperature can be employed as long as it is sufiicient to produce water introduced into the conveyor housing 31 assists in cooling the purified soap stock therein to render the soap stock pumpable and additional alkali mixed with a heated stream ofthe soap stock by delivering an alkali solution a flowable mixture. The preferred alkali is caustic soda although in the present process other plete saponification may be attained therein. By

maintaining the agitators l'l running during withdrawal of the soap stock mixture from the mixer III a substantial uniform mixture may be delivered to the coil l 6 by the pump l5.

This mixture is subjected to high temperatures and pressure in the coil l6 and then pumped through one ormore coils 22 where it is additionally subjected to high temperature and pressure conditions. For example, the pressure in coils l6 and 22 may range between 250 to 1,000 pounds per square inchnand the temperature reached in coil 22 may be as high as 450 to 700 through the pipe 49 to a flow mixer'50 positioned F. A preferred temperature and pressure in coil 22 is approximately 550 F. and 400 pounds per square inch. By subjecting the soap stock mixture to these high temperatures under conditions of flow in the coils l6 and 22 the saponifiable materials in the soap stock mixture are substanvaporizable in the evaporating chamber 25 and other material, such as certain amino acids or amides, will combine with the alkali to produce materials having excellent detergent properties or are water soluble such that the treated soap stock may be given a subsequent washing with water to remove such water soluble impurities. Sufficient time is provided for the breaking down of such compounds which can usually be accomplished in periods of time ranging from 2 to 10 minutes. This will vary with difierent soap stocks and the time necessary for a patricular material can be determined by experiment and one or more coils 22 employed of sufiicient length to provide the necessary time of treatment. 7

When the heated mixture is discharged into the evaporating chamber 25 under reduced pressure the vaporizable material, such as ammonia and amines as well as water, is vaporized and withdrawn from the evaporating chamber through the pipe 26. Any glycerine present in the mixture is also vaporized and withdrawn. It is preferred to maintain the evaporating chamber under vacuum conditions by employing condensers such as 21 and 29 and the vacuum pump 3|.- Best results are obtained by employing a vacuum as high as commercially practicable, and vacuums ranging from approximately 27 to 29 inches of mercury are suitable. The temperature of the material as discharged into the evaporating chamber is preferably high enough to maintain the resultant purified soap stock in liquid condition even though substantially all of the water and other vaporizable materials have been withdrawn therefrom. The liquid purified soap stock flows down the heated walls of the evaporating chamber and the temperature in the evaporating chamber is maintained sufliciently high to retain the purified soap stock in molten condition. Thus temperatures ranging from 420 to 600 F. can be employed depending upon the nature of the soap stock being treated and usually this temperature may be as low as 475 F. without causing solidification of the purified soap stock upon the walls of the evaporating chamber. To insure that all of the vaporizable materials are liberated in the evaporating chamber 25 the pressure in the last coil v22 may in some cases be sufilciently low that, at the temperature maintained therein, some vapors are formed in the coil so that the heat necessary for this vaporization is supplied in the coil rather than in the vaporizing chamber 25.

The condensible vaporizable materials, such certain amines, as well as a small proportion of glycerine present in the soap stock, may be condensed in the condensers 21 or 29 and iffisufficient cooling is employed any ammonia may be retained in water condensed in these condensers.

The condensed materials are collected in any desired fractions in the receivers 28 and ill and may be withdrawn therefrom through pipes 29' and 30' by any suitable means such as pumps cation.

The purified soap stock, which consists essentially of soap along with other detergent materials, ls cooled and discharged by the conveyor 38 without breaking the vacuum in the evaporating chamber 25. This material is substantially anhydrous and free of vaporizable materials and is also substantiallyodorless and free from materials which will cause subsequent deterioration of soap made therefrom. The material may be shipped or stored for indefinite lengths o time without deterioration.

If desired, the soap stock mixture in the mixer It] may be washed and treated with salt or sufficient caustic soda to cause a separation of soap and impurities in a manner similar to that employed in soap making processes before the soap stock mixture is introduced into the heating coil 16. Thus one or more separations may be accomplished in the mixer 10 by washing and salting out impurities and allowing the same to settle as soap lyes which may be withdrawn through the pipe l5 and discarded. Such operation is ordinarily not necessary with most soap stocks and entails a loss of soap, reagents and valuable by-products.

As before stated, the additional caustic soda or other alkali. may be supplied continuously through the pipe 49 in which case substantially instantaneous sapO-m'fication of the saponifiable materials in the soap stock is effected because of the high temperatures in the mixer 50 and the rapid and efficient mixing accomplished at these high temperatures. Thus the soap stock may be heated to temperatures between approximately 300 and 420 F. in the coil IS without causing decomposition of unsaponified glycerides or fatty acids therein. Also as indicated above, a mixture of high quality soap and water may be introduced into. the conveyor housing 31 to assist in cooling the purified soap stock from the evaporating chamber 25, and to produce a hydrated soap containing sufiicient moisture for the production of bar soap. It is apparent that if the particular soap stock being treated and the proportions of soap stock in the resultant mixture require more moisture than that which can be contained in a mixture of soap and water capable of being handled by the conveyor 41, a pump may be employed in lieu of the conveyor 41 for delivering a liquid mixture of soap and water into the conveyor housing 31. By balancing the amount of soap introduced and its moisture content against the amount of substantially anhydrous purified soap stock delivered by a conveyor 38, a properly hydrated soap product can be extruded from the conveyor housing 31. It is found that high grade soap products which will not deteriorate with age can be produced containing as high as 40 to purified soap stock. 4

It is also possible to form the additional soap mixed with the purified soap stock as part of the process. Thus desired amounts of saponifiable materials such as fatty acids or glycerides along with proper proportions of alkali can be introduced into the mixer H1 or during flow of' mixed with the purified soap stock. Fatty acids are more suitable for this purpose than glycerides as valuable glycerine liberated from the glycerides is recovered in admixture with other materials and must be separated therefrom.

The process is also adaptable for treating soap stock without the addition of additional alkali.

By merely adding 'water through thepipe to the mixer l0 and passing the resultant mixture through the heating devices It and 22 under high pressure and temperatures the water will react with neutral oil to cause the same to split into fatty acids and glycerine and the proteins and other impurities will be broken down into simpler compounds as is the case when additional caustic is employed. The fatty acids and glyc erine can be vaporized in the evaporating chamber 25 and distilled over into the condensers 21 and 29 and recovered with other vaporizable materials. Also by subjecting the mixture to somewhat less drastic temperatures in the coils i6 and 22 substantially all of the watermay be removed from the soap stock as well as other vaporizable materials without to any great extent breaking down the glycerides, proteins, etc., so that a substantially dehydrated and cooled soap stock is extruded by the conveyor 38. Such soap stock, being substantially anhydrous, can also be stored for extended periods of time or shipped without deterioration, but is in general not suitable for incorporation into high quality soaps unless further treated. In this case it is apparent present time of very little value, can be converted into a valuable material capable of being incorporated into high quality soaps and at the same time valuable by-products can be recovered therefrom. Also the invention may be employed merely to dehydrate the soap stock and stabilize the same so that it can be stored and shipped to points further distant than heretofore without fermentation or other deterioration. In this connection it is noted that the dehydrated soap stock is of much less weight and can be handled in ordinary containers instead. of sealed drums as was necessary with untreated soap stock. When the soap stock is subjected tothe preferred process of the present invention, -it results in a purified soap stock product which, is sub.- stantially free of disagreeable odor and-impurities such as proteins, phosphatides, and other deleterious materials, as well as having a much lighter color than the original soap stock,

While I have described the preferred embodiments of my invention it is understood that I am not to be limited to the details thereof but that the invention may be varied within the scope of the following claims.

What I claim is:

1. The process of purifying soap stock from the alkali refining of vegetable and animal oils containing proteins and other unsaponifiable impurities, which comprises, the step of heating said soap stock under conditions which substantially prevent local overheating to a temperature suflicientlyhigh to break at least a portion of said proteins and other impurities into simpler compounds capable of being removed from said soap stock as vapors, maintaining said soap stock during heating to high temperature under sufficient conditions of movement to prevent local overheating and burning of said impurities, removing said vapors to form a purified soap product, and cooling said product before the same is damaged by said temperature. v

2. The process of treating soap stock containing unsapom'fiable impurities including proteinaceous materials from the alkali refining of vegetable and animal oils, which comprises, mixing suflicient alkali and water with said soap stock to saponify substantially all of the unsaponified saponifiable materials contained in said soap stock and to form an easily flowable mixture, pumping said mixture through a heating zone under pressure, supplying sufficient heat in said heating zone to break at least part of the unsaponifiable impurities in said soap stock into simpler compounds, maintaining sufiicient movement of said materials during heating thereof to prevent local overheating and burning of said im-- purities, thereafter reducing the pressure upon said mixture to vaporize certain of said compounds and produce a substantially completely saponified soap substantially free of odorous and decomposable impurities.

3. The process of purifying soap stock 'containing unsaponifiable impurities including proteinaceous materials from the alkali refining of vegetable oils, which comprises, mixing sufiicient alkali with said soap stock .to saponify substantially all of the unsaponified, saponifiable materials contained therein, mixing suflicient water with said soap stock to form a fiowable mixture, pumping said mixture continuously through a heating zone under pressure, supplying suificient heat to said heating zone to raise the temperature of said mixture to a temperature which will cause the decomposition of at least a portion of said impurities contained in said soap stock into simpler compounds capable of being vaporized from said soap stock or of combining with said alkali to form relatively stable compounds having detergent properties, maintaining sufficient movement of said mixture during heating of said mixture to prevent local overheating and maintain a substantially uniform mixture therein and thereafter vaporizing water and certain of said compounds from said soap stock to produce a substantially completely saponified soap mixture substantially free of odorous and decomposable compounds.

4. The process of treating soap stock contain- ,ing unsaponifiable materials including proteisure is reduced, thereafter reducing said pressure and, removing said water from said soap stock in vapor form to produce a substantially dry soap stock which may be stored and shipped without decomposition.

5. The process of purifying soap stock contain ing proteins from the alkali refining of vegetable and animal oils, which comprises, mixing sufiicient water with said soap stock to form a flowable mixture, subjecting said soap stock to a temperature and pressure sufficient to break down proteins contained in said soap stock into simpler compounds and cause glycerides present in said soap stock to split into glycerine and fatty taining unsaponifiable impurities including proteinaceous materials from the alkali refining of vegetable and animal oils, which comprises, mixing sufficient alkali therewith to substantially completely saponify unsaponifiedsaponifiable materials contained therein, heating the resultant mixture under conditions of agitation to a temperature sufficient to substantially completely saponify all of said saponifiable materials, thereafter heating the resultant mixture to a temperature sufiicient to decompose at least a part of the impurities contained in said soap stock into vaporizable compounds while maintaining said resultant mixture under sufllcient conditions of movement during said heating to prevent local overheating and burning of said unsaponifiable impurities, and thereafter removing said compounds in vapor form from said soap stock.

' 7. The process of purifying soap stock, containing unsaponifiable impurities including protei-' naceous materials from the alkali refining of vegetable and animal oils, which comprises, mixing sufficient water therewith to form a iiowable mixture, pumping said mixture through an elongated heating zone under pressure between 250 and 1,000 pounds per square inch, supplying suf-' ficient heat o said mixture in said heating zone to raise the temperature thereof between approximately 450 and 700 F., maintaining sufficient movement of said mixture during said heating to prevent local overheating and burning of said impurities, discharging the heated mixture into an evaporating chamber, maintaining a vacuum in said chamber to cause separation of vaporizable materials fromsaid soap stock, and continuously withdrawing said vapors from said evaporating chamber so as to deposit in said evaporating chamber a substantially anhydrous soap mixture which is substantially free of odorous and decomposable materials.

8. The process of purifying soap stock containing proteinaceous impurities from the alkali refining of vegetable and animal oils, which comprises, mixing suflicient alkali and water therewith to saponify substantially all, of the unsaponifled saponiflable materials contained in said soap stock and form a fiowable mixture, maintaining said mixture substantially uniform and pumping the same under pressure through a heating zone, supplying sufilcient heat to said heating zone to break down proteinaceous impurities contained in said soap stock into ammonia, amines, peptides, amino acids and similar compounds which are vaporizable or will combine with said alkali, maintaining sufiicient movement of said mixture during said heating to prevent local overheating and burning of said impurities, discharging the resulting mixture from, said heating zone into an evaporating chamber having a vacuum therein, maintaining sufl'icient temperature in said evaporating chamber to cause separation of water and said vaporizable materials from said resultant mixture and cause deposition of substantially anhydrous soap stock free from vaporizable materials in said chamber in molten form, continuously removing said vapors from said evaporating zone and condensing at least a portion thereof so as to maintain said vacuum and recover valuable by-products, and continuously removing a substantially completely saponifled soap stock consisting essentially of soap stock andother detergent compounds without breaking said vacuum.

BENJAMIN H. THURMAN. 

